The analog TV bands included the Very High Frequency (VHF) band and the Ultra High Frequency (UHF) band. VHF is composed of the low VHF band operating from 54 MHz to 88 MHz (excluding 72 MHz to 76 MHz), and the high VHF band operating from 174 MHz to 216 MHz. The UHF band is composed of the low UHF band operating from 470 MHz to 698 MHz, and the high UHF band operating from 698 MHz to 806 MHz
In the United States, the Federal Communications Commission (FCC) set Jun. 12, 2009 as the deadline for replacing analog TV broadcasting by digital TV broadcasting. The digital TV channel definitions may be the same as the analog TV channel. The digital TV bands may use analog TV channels 2 to 51 and may not use 37, while the analog TV channels 52 to 69 may be used for new non-broadcast users. The frequency allocated to a broadcasting service but not used locally may be referred to as White Space (WS). TV White Space (TVWS) may refer to the TV channels 2 to 51, which may not include except 37.
Besides TV signals, there are other licensed signals that may be transmitted on the TV bands. Channel 37 may be reserved for radio astronomy and Wireless Medical Telemetry Service (WMTS), where the latter may operate on any vacant TV channels 7 to 46. The Private Land Mobile Radio System (PLMRS) may use channels 14 to 20 in certain metropolitan areas. Remote control devices may use channels above channel 4, except channel 37. The starting frequency of FM channel 200 is 87.9 MHz, with partial overlapping on TV channel 6. The wireless microphone may use channels 2 to 51 with a bandwidth of 200 kHz.
As a result of the transition from analog to digital TV transmissions, certain portions of the spectrum may no longer be used for TV transmissions, though the amount and exact frequency of unused spectrum may vary from location to location. The FCC has opened up these TVWS frequencies for a variety of unlicensed uses.
The opportunistic use of unlicensed bands, such as TVWS bands, may be exploited by secondary users for any radio communication given that the use does not interfere with other incumbent and/or primary users. There are many problems associated with LTE, and other cellular technologies, use of unlicensed spectrum such as TVWS.